a. Field of the Invention
The invention relates to a safety apparatus in an automatic transmission apparatus for a vehicle, such as a motorcar or the like.
B. Prior Art
An automatic transmission apparatus is known in which a high speed clutch is interposed in a high speed power transmission system and a low speed clutch is interposed in a low speed power transmission system and the clutches are selectively connected to an oil pressure source such as an oil pressure pump of the like through a shift valve responsive to a comparison value between engine output power and vehicle speed. This conventional arrangement is deficient in that, for instance, during the time when the high speed clutch is supplied with pressure oil and the vehicle runs at high speed, if the shift valve is accidentally changed over to the other side and thereby the low speed clutch is supplied with pressure oil and is brought into its operating condition, there is caused the danger of a sudden engine braking operation, engine overrunning or the like.